1. Field of the Invention
The present invention relates to a web separating device. More particularly, the present invention relates to a web separating device for cutting web into two web sections, and capable of the cutting separating operation reliably and with a simplified structure.
2. Description Related to the Prior Art
Film of polymer is produced by solution casting or film casting. A term of web is used as a product of film casting, in particular when the film is film web of optical film. A producing line of the web is constituted by apparatuses and elements grouped in four sections, which are for film casting, film orienting, drying, and winding.
If the processes of the component apparatus are connected with continuity, occurrence of an error or failure in the middle of the producing line must cause a stop of the entirety of the producing line. This makes it unable to manage an amount of supply of dope as liquid material of polymer. Restarting the normal operation of the producing line requires considerably long time and high cost. In consideration of coping such a problem, a web separating device for web cutting is known, in which web is cut while transported continuously, to form an upstream web section and a downstream web section. The upstream web section is wound by a winder. The use of the web separating device enables an upstream positioned apparatus to continue operation even when a problem occurs in a downstream positioned apparatus. When the problem is solved, the upstream and downstream web sections are joined with one another, to set the producing line in the continuous state.
Furthermore, the web separating device is generally used for changing over from a process continuous state of continuity of the respective processes in the producing line to a process disconnected state in which the various processes are separate from one another. After the cutting into the upstream and downstream web sections, the upstream web section is wound by a winder. The downstream web section is provided with an advancing guide leader attached to a rear end thereof, and transported to the downstream positioned apparatus. There is a web roll or leader roll previously loaded in an advancing device. The advancing guide leader in a long form is advanced from the web roll to the downstream positioned apparatus. Furthermore, it is possible to use the web separating device in changing over from the process disconnected state to the process continuous state. At this time, the web separating device is used for joining the upstream and downstream web sections extending through respectively the upstream and downstream positioned apparatuses, so the process continuous state is set again for the producing line. Accordingly, the web separating device of the known type has performance for separation and joining.
JP-A 1-178957 discloses a known type of the web separating device. The web separating device includes a joining drum, a cutter roller, and first and second joining rollers. The joining drum includes a suction mechanism and a guide roller. The first joining roller is supported on a shiftable arm. The joining drum and the cutter roller cooperate together to cut the web. The upstream web section obtained from the web is attached to the advancing guide leader which is retained on the first joining roller.
However, the web separating device according to JP-A 1-178957 has shortcomings in that the first joining roller is shifted to a predetermined position in synchronism with the joining drum, and also must be rotated upon discontinuing the suction of the advancing guide leader. Difficulties in the operation are extremely high because even a complicated combination of movement requires high precision in successive steps.
It is likely that the advancing guide leader adheres incidentally to the downstream web section should the shift of the first joining roller be too early, or should rotation of the first joining roller start too early. A further problem lies in an error in the positioning of the front end of the upstream web section outside the web path in the web transport after the joining, should the shift of the first joining roller be too late, or should rotation of the first joining roller start too late. Due to various errors, the web is likely to be broken accidentally. To solve such problems, use of a certain motor with high performance or a suction mechanism with quick response may be conceived. However, a control system associated with such elements for joining operation inevitably require a high cost of manufacture, and not consistent with a low manufacturing cost.